The blue swimmer crab resource is accessed by the commercial and recreational sectors. The Department of Primary Industries and Regional Development manages both together to ensure sustainable fisheries.
WA’s annual blue swimmer crab commercial catch usually exceeds 500 tonnes. Hundreds of tonnes are also caught by recreational fishers, especially in the populous metropolitan region.
We manage fishing through measures including commercial licences and area and seasonal crabbing closures. A minimum legal size limit of 127 mm ensures crabs can spawn at least once before they can be taken.
South West management
A 2018 review of the South West Blue Swimmer Crab resource, which extends from Perth to Cape Naturaliste, found measures were not adequately protecting breeding stock across the resource. In response, new measures have been implemented to protect the stock including:
- A three month closure to recreational and commercial crabbing from 1 September to 30 November each year in all coastal waters, rivers and estuaries from the Swan and Canning Rivers to Minninup Beach (15 km south of Bunbury).
- A bag limit of five crabs per fisher for the Swan and Canning Rivers.
- A maximum of 5 females in Geographe Bay (as part of the 10 crab bag limit).
- Closure of the commercial crab fisheries in Warnbro Sound and in oceanic waters between Mandurah and Bunbury.
Concern about stocks in Cockburn Sound resulted in
Cockburn Sound being closed to crabbing from 2014. A new stock assessment in
2024 indicated that the stock could support a low level of catch. More
information is provided in the Cockburn Sound blue swimmer crab science update.
Informed
by the new assessment, limited recreational crabbing will resume in Cockburn
Sound from 1 December 2024. More information is available in the Cockburn Sound flier.
During the closed season, it is illegal to fish for or be in possession of blue swimmer crab in the closed waters.
Shark Bay management
The
Shark Bay blue swimmer crab resource is harvested commercially by the Shark Bay
Crab Managed Fishery (SBCMF), which consists of Shark Bay crab trap, Shark Bay
prawn trawl, and Shark Bay scallop trawl operators. This crab stock also
supports a regionally important recreational fishery (<5 t). The commercial
sector is managed under an Individual Transferable Quota (ITQ) management
system under the Shark Bay Crab Managed Fishery Management Plan 2015 and
Blue Swimmer Crab Resource of Shark Bay Harvest Strategy 2020.
In
2017 the Shark Bay Crab Working Group was established. The Working Group, which
includes DPIRD, commercial and recreational fishing representatives provides a
forum to discuss SBCMF management, including TACC reviews.
Shark
Bay crab stocks are assessed as part of a multi-species fishery-independent
surveys conducted in February, June and November each year. In late 2011, Shark
Bay crab stock experienced a significant decline following an extreme 2011
marine heatwave. After ocean surface temperatures reached 4-5ºC above average,
few young crabs survived therefore the fishery was closed for 18 months over
2012/2013 to promote stock recovery. Limited commercial fishing resumed under a
notional quota management system for the 2013/14 (400 tonne) season and as
stock continued to recover, the TACC increased to a maximum of 650 t in
2021/22. Stock levels, catches and TACCs have fluctuated in recent years with a
400 t TACC set in 2023/24 and 500 t TACC set in 2024/25.
The
current stock assessment indicates that spawning, recruitment and biomass
levels have been increasing steadily under increasing catch levels and
favourable environmental conditions.
Monitoring, assessment and research
To
protect stocks into the future, we monitor the status of blue swimmer crab
populations and fishing levels.
We
use various methods to monitor crab stocks including trapping and trawling
surveys which provide information about the abundance, size and reproductive
condition of the animals in each population.
Another
method is collecting data about effort and catch rates on board commercial
vessels. Research staff measure the retained and non-retained catch. We also
make estimates of recreational catch and effort from fishing surveys.
By
analysing catches and comparing this information with blue swimmer crab biology
and the size and gender structure of the population being fished, researchers
are able to draw conclusions about stock status.
Research
is continuing into the relationship between different blue swimmer crab
populations. This requires an understanding of growth and movement patterns,
and the impact of human activities and environmental factors on breeding and
growth.
The most recent information on the performance of the blue swimmer crab
fisheries can be found in the annual State of the Fisheries Reports.